Field of the Invention
The present invention relates generally to security systems for residential or commercial buildings, and more particularly to an electrical or electronic security system which prevents an entrance door to the building both from being locked without first activating the security system, and from being unlocked without first deactivating the security system.
One of the seemingly inevitable consequences of our increasingly crowded urban society has been an ever-increasing crime rate, or at least the threat thereof. Breaking and entering and burglary have become increasingly common occurrences, affecting both residential property and commercial property. Accordingly, the sale and installation of various security systems, commonly known as burglar alarms, has become a thriving business as many property owners seek to discourage crime to property through the use of such systems.
The typical system for use to safeguard a building has five basic elements: a control unit, a power supply for powering the system, a main on/off switch, one or more sensors to detect illicit entry, and means for providing an alarm or other indication of the occurrence of unauthorized entry. The control units are electrical, or, more typically, electronic systems of considerable sophistication. Power supplies generally are connected to AC line voltage, with a DC battery backup. The main on/off switch is typically a numerical keypad, although in some cases key locks may be used. The sensors include devices to detect the opening of a door or window, pressure pads, and optical or sonic sensors. The alarm may be provided audibly, through the use of a horn or bell, or electronically to the police or to a security company to cause the police or security guards to promptly descend on the building to investigate the alarm.
There exist two major problems with alarm systems for use with buildings, and both are very basic problems. The first, and most serious, is the problem of remembering to activate the security system upon leaving the building. The second problem, also serious, is remembering to deactivate the system prior to entry into the building.
With regard to the first problem of remembering to arm the security system, it is almost inevitable that people will forget to activate the security system when leaving from time to time. The omission may occur accidentally through oversight, or it may occur deliberately, but in either event the all too frequently result is an illegal entry and property loss. It is accordingly a primary objective of the present invention to provide a system which will require the alarm system to be set without fail, each time the building is to be left by its inhabitants.
As might be expected, the art is not silent as to improvements and innovations encouraging the setting of the alarm system. Unfortunately, most such systems are intended for use with automobiles rather than with dwellings. Examples of such systems are illustrated in U.S. Pat. No. 3,936,673, to Kelly et al., in U.S. Pat. No. 4,225,008, to Colell et al., and in U.S. Pat. No. 4,635,035, to Ratzabi. All three of these systems use a combination lock and switch, with the car being locked or unlocked, and the alarm being simultaneously activated or deactivated with a key.
The Kelly et al. device teaches the basic concept, while the Colell et al. and Ratzabi devices go further and provide authorized keys which may perform both functions, while nonauthorized keys will merely lock or unlock the lock of the car, and not deactivate that alarm system. The basic problem with these systems is that a person who is adept at locks may gain entry to the vehicles, deactivating the alarm systems by picking the lock. While such systems are obviously better than no security system, they do not provide optimal security.
A similar system for use with buildings is disclosed in U.S. Pat. No. 4,370,644, to Droz. The Droz system has a switch operated by a sliding bolt in the door, and has the same problem as the other systems described above- namely that an intruder need only pick the lock to both gain entry and to disarm the security system. Today, most sophisticated security systems, both for automobiles and for dwellings, use numerical keyboards as the deactivation device (and also frequently as the activation device). As such, the security system may not be deactivated by merely picking the lock.
It is therefore an objective of the present invention to provide a security system which will not be capable of being deactivated by merely picking the entry lock. In addition, an improved system should also be set each time the building is left (at least for an extended period), or when the building is left in a locked condition. The improved system must not depend on being set by a person leaving the building. A number of automobile systems have an automatic setting feature initiated by removing the key from the ignition, but security systems for dwellings do not have such a feature. The automatic setting of the security system should not be initiated by merely locking the entry door, since entry doors of dwellings are commonly locked with the inhabitants inside.
The second major problem, namely of remembering to deactivate the security system, does not present the threat of property loss in the event of a failure to deactivate the system prior to entry. Rather, the problem presented is that of a false alarm occurring when someone forgets to deactivate the security system. The problem is annoying when forgetting to deactivate the system sets off a horn or bell, particularly at night when neighbors may be sleeping. It is minimal, however, since, the security system can usually be turned off quickly.
The problem is exacerbated when the alarm is provided to the police or to a private security agency, generally resulting in an armed patrol descending on the building. This may present a dangerous situation to the authorized person, who may be mistaken for a criminal. It is also expensive, since both the police and security agencies may charge for false alarms.
One of the solutions the art has provided to this problem is the provision of a low level alarm within the building for a short time to remind the person forgetting to deactivate the security system that the system is still on. This is at best a pseudo-solution to the problem, since it will also act as a warning to an illicit intruder. It is accordingly a primary objective of the present invention to provide a security system which will be deactivated prior to entry of the building.
Such a system must not be deactivated merely by unlocking the entry door, but rather must possess an independent deactivation mechanism. In addition, the system must absolutely prevent the building from being entered prior to the security system being deactivated. The system which is a solution to the problems enumerated above must also possess several other attributes. It must be both effective and easy to use, and is preferably of an unsophisticated design both to make it economic of manufacture and highly reliable. It must also eliminate all of the above problems and achieve all of the desired advantages and objectives without incurring any relative disadvantage.